1. Field of the Invention
This invention relates to engageable coupling assemblies having reduced spin losses and methods of assembling such assemblies within automotive transmissions to reduce such losses.
2. Background Art
One-way clutches are commonly employed in automatic transmissions for automobiles. A one-way clutch allows a first clutch plate to free-wheel in a first rotational direction relative to a second clutch plate, and to clutch in a second rotational direction. Examples include roller clutches and sprag clutches.
As transmission efficiency has become increasingly more important over the last several years, many transmission manufacturers have started to make specifications regarding the amount of torque it takes to spin a one-way clutch during overrun conditions (i.e. spin loss).
U.S. Pat. No. 5,597,057 discloses a one-way clutch apparatus comprising a driving member having a plurality of recesses, a corresponding plurality of biasing members disposed in the recess, a corresponding number of keys or struts disposed over the biasing members in the recesses, and a driven member having a plurality of key-engaging notches formed circumferentially about an inside surface. Each of the keys includes a pair of laterally protruding arm portions and each of the arm portions has a ramp formed thereon which acts as a relief to allow the inside surface of the driven member to be placed to close proximate relationship with the inside surface of a driving member and to overlay portions of the recess. The overlaying enables the driven member to damp or otherwise limit the movement of a back end portion of each key when the driving member is moved in either a free-wheeling direction or driving direction, while the ramp portions allow a front end portion of the key to be urged outwardly without any portion of the arm portion interfering with the inside surface of the driven member overlaying portions of each recess. The one-way clutch apparatus is not as dependent upon a copious and continuous supply of lubricant to damp unwanted movement of the key.
U.S. Pat. No. 5,964,331 discloses an overrunning clutch assembly including first and second ring-shaped clutch members with face surfaces disposed in opposing relation and with at least one rigid strut disposed therebetween for movement to engage recessed pockets in the opposed surfaces upon rotation in one direction and for movement out of engagement with the pockets in at least one of the face surfaces upon relative rotation in the opposite direction. A retaining member permanently retains the clutch in assembled relation and cooperates with the ring-shaped clutch members to form a lubricant reservoir maintaining the struts in a lubricant bath during operation. The retaining member forms a weir over which the lubricant flows from the reservoir at a radial location to assure that the struts remain submerged during operation.
U.S. Pat. No. 6,186,299 discloses an overrunning coupling assembly includes a notch plate and an annular coupling pocket plate positioned in face-to-face relationship with respect to each other along a common axis. The pocket plate has strut pockets disposed at angularly spaced positions about the common axis. The notch plate has notch recesses at angularly spaced positions about the common axis and positioned in juxtaposed relationship with respect to the strut pockets. Torque-transmitting struts are positioned in each of the strut pockets. Each strut has first and second ears at one edge thereof for enabling pivotal motion of the struts about an ear axis intersecting the ears. The opposite edge of each strut is movable between disengaged and engaged positions with respect to one of the notch recesses whereby one-way torque transfer may occur between the plates. A lubricant flows between the notch plate and pocket plate. A spring is positioned in each strut pocket and biases the respective strut toward the notch plate. Each spring engages the respective strut intermediate the ear axis and the opposite edge. Each strut pocket provides sufficient clearance forward of the respective opposite edges of the strut to allow forward sliding movement of the respect strut during overrunning to cause the engagement of the respective spring and strut to occur nearer the ear axis, thereby reducing the length of a moment arm about which the spring acts upon the strut which enables frictional forces of the flowing lubricant to hold the strut in its disengaged position to prevent the strut from slapping against the notch recesses as the notch plate and pocket plate are respectively counterrotated.
U.S. Pat. No. 7,455,157 discloses an overrunning clutch including a cam plate formed with cams angularly spaced about a central axis, and a rocker plate that includes pockets angularly spaced about the central axis. Each pocket includes a first concave surface having a center located within the pocket and through which a pivot axis passes. Each pocket contains a rocker that includes a first convex surface complementary to, and at least partially surrounded by the first concave surface. Springs, supported on the rocker plate, each urge a rocker to pivot about the pivot axis toward the cam plate. In one embodiment, hydraulic lubricant present on a cam surface becomes located between the cam surface and a radial outer surface of the rocker, thereby dampening or cushioning contact between the rocker and the cam. As the rocker ratchets on the cams, lubricant located on a cam surface and an undercut surface is compressed by the ratcheting motion of the rocker and is pumped axially away from a radial flange of the cam plate and the cam surfaces to a journal surface. This pumping action, which occurs when each of thirty-seven cams ratchet over seven rockers per revolution of the cam plate relative to the rocker plate, provides continuous lubricant flow to the journal surface of the cam plate and the mating journal surface of the rocker plate.
U.S. Pat. No. 7,766,144 discloses a clutch plate assembly having a friction interface and internal fluid passages for delivering pressurized fluid to the friction interface to cool the interface, and to reduce spin losses through the clutch assembly. The fluid passages comprise a plurality of primary passages extending inward from a clutch plate inner or outer diameter, and a plurality of secondary fluid passages intersecting the primary fluid passages for conducting fluid to the friction interface. Fluid is directed to the friction interface during clutch engagement for cooling thereof when the clutch assembly is engaging, and separates the clutch plates to reduce spin losses when the clutch assembly is disengaged. A method is also provided for controlling fluid flow at the friction interface, including providing fluid directly to the interface for cooling when the clutch plate assembly is engaging, and for reducing spin losses when the clutch plate assembly is substantially disengaged.
For purposes of this application, the term “coupling” should be interpreted to include clutches or brakes wherein one of the plates is drivably connected to a torque delivery element of a transmission and the other plate is drivably connected to another torque delivery element or is anchored and held stationary with respect to a transmission housing. The terms “coupling”, “clutch” and “brake” may be used interchangeably.
Other patent references related to the present invention include U.S. patents and published applications: U.S. Pat. Nos. 5,918,715; 6,193,038, 6,283,265; 6,830,531; 2009/0045024; and 2009/0118933.
Despite the above prior art, there is a need to reduce the torque required (or spin loss) to spin a one-way clutch during overrun conditions.